As far we know and examined in the sources this Missa pro defunctis is not complete it could consists out of the following movements:
01. Introito - Requiem aeternam
02. Kyries - Kyrie, Christe, Kyrie
03. Gradual - Requiem Aeternam
04. Secuencia - Dies Irae plainchant
05. Offertorio - Domine Jesu Christe
06. Sanctus - Sanctus y Benedictus
07. Agnus Dei - Agnus Dei
08. Communio - Lux aeterna

This Misa de Difuntos is set by Nicolás de Santa Maria for double choir in coro spezzato style for SAT coro I and SATB coro II with figured basso continuo and contra bajo.
From the gradual "Requiem aeternam" only the verse "In memoria aeterna" has been set to music. From the sequence "Dies irae" the first four measures have been set to music and the last measures.
That means the coro I could alternate with the odd verses and the other choir could sing the even plainchant verses.
In the Offertorio one Tiple has been added to coro I, also this movement is written for SSAT coro I and SATB coro II.
This Missa pro defunctis can be found in the Archivo Musical del El Escorial Madrid no 37891 in the Catalogo del Archivo del Monasterio de San Lorenzo El Real de El Escorial page 111 no. CC 3 and page 462 no.1480.

As far we know and examined in the sources this Missa pro defunctis is complete it could consists out of the following movements:
01. Introito - Requiem aeternam
02. Kyries - Kyrie, Christe, Kyrie
03. Gradual - Requiem Aeternam
04. Secuencia - Dies Irae plainchant
05. Offertorio - Domine Jesu Christe
06. Sanctus - Sanctus y Benedictus
07. Agnus Dei - Agnus Dei
08. Communio - Lux aeterna

This Misa de Difuntos is set by Nicolás de Santa Maria for double choir in coro spezzato style for SAT coro I and SATB coro II with figured basso continuo and contra bajo.
From the gradual "Requiem aeternam" only the verse "In memoria aeterna" has been set to music. That means the belonging “Requiem aeternam dona eis Domine: et lux perpetua luceat eis” will be performed in plainchant. From the Sequentia "Dies irae" the first four measures have been set to music and the last measures. That means the coro I could alternate with the odd verses and the other choir could sing the even plainchant verses.
The Introitus and Kyrie are set in F-Major. The Gradual is set in b-minor . The Sequentia is set in the Lydian mode and is not based on the traditional melody. Sanctus-Benedictus, Agnus Dei and Lux aeterna are set again in F-Major.
This manuscript consists out of 26 folio pages. This Missa pro defunctis can be found in the Archivo Musical del El Escorial Madrid no 37891 in the Catalogo del Archivo del Monasterio de San Lorenzo El Real de El Escorial page 111 no. CC 3 and page 462 no.1489.

This Misa de difuntos a 8 consists out of the following movements:

01. Introito - Requiem aeternam
02. Kyries - Kyrie, Christe, Kyrie
03. Gradual - Requiem Aeternam
04. Sequencia - Dies Irae plainchant
05. Offertorio - Domine Jesu Christe
06. Sanctus - Sanctus y Benedictus
07. Agnus Dei - Agnus Dei
08. Communio - Lux aeterna

This Misa de difuntos is set by Nicolás de Santa Maria for double choir in coro spezzato style for SSAT coro I and SATB coro II, con choro de violinos (VL 1, VI 2) with basso continuo. Both choirs have two violins (VI 1 and V I 2) setting.
From the gradual "Requiem aeternam" only the verse "In memoria aeterna" has been set to music, and is set with four violins. That means the belonging “Requiem aeternam dona eis Domine: et lux perpetua luceat eis” will be performed in plainchant. From the sequence "Dies irae" the first ten, twelfth, thirteenth and the last two verses have been set to music, the other verses can be sung in plainchant.
The offertory "Domine Iesu Christe" has no verse ‘Hostias et preces’ that means this verse could be sung in plainchant. There are no scores available but it is interesting to research whether the two eight voices Masses have some connexion. Samuel Rubio (O.S.A.) (1912-1986) the famous author of the Catálogo del Archivo de Música del Monasterio de San Lorenzo el Real Escorial didn’t give any suggestion in that way. This Missa pro defunctis can be found in the Archivo Musical del El Escorial Madrid no 39843 and in the Catalogo del Archivo del Monasterio de San Lorenzo El Real de El Escorial page 460 no. 1481.

This Misa de Requiem a 8 consists out of the following movements:

01. Introito - Requiem aeternam
02. Kyries - Kyrie, Christe, Kyrie
03. Gradual - Requiem Aeternam
04. Secuencia - Dies Irae plainchant
05. Offertorio - Domine Jesu Christe
06. Sanctus - Sanctus y Benedictus
07. Agnus Dei - Agnus Dei
08. Communio - Lux aeterna

This Misa de Requiem is set by Nicolás de Santa Maria for double choir in coro spezzato style for SSAT coro I and SATB coro II, con choro de violinos (VI 1, V I 2) with basso continuo.
In the heading of this Requiem is a special request. This Misa is composed to be sung in the Real Monasterio El Escorial San Lorenzo set by Nicolas de Santa Maria . From the gradual "Requiem aeternam" only the verse "In memoria aeterna" has been set to music, and is set with four violins. That means the belonging “Requiem aeternam dona eis Domine: et lux perpetua luceat eis” will be performed in plainchant. From the Sequentia "Dies irae" the first ten, twelfth, thirteenth and the last two verses have been set to music, the other verses can be sung in plainchant.
The offertory "Domine Iesu Christe" has no verse ‘Hostias et preces’ that means this verse could be sung in plainchant.
This Missa pro defunctis can be found in the Archivo Musical del El Escorial Madrid no 39841 and in the Catalogo del Archivo del Monasterio de San Lorenzo El Real de El Escorial page 460 no. 1479.

This motet “Rex tremendae majestatis” is in general a part of the Sequentia “Dies Irae”, Liber Usualis (edition 1936, page 1811) and is set by Nicolás de Santa Maria for SATB with figured basso continuo. The motet is set in F-major. The title of this motet is taken from the cover of the of the part Basso continuo.
This score has five unnumbered pages, formed by folios folded in two. The part of the Basso continuo was used as a cover the ensemble, it consists out of the parts: Tiple (1 f.), alto (1 f.), tenor (1 f.), bass (1 f.) basso continuo (1 f.).
This motet can be found in the Archivo Musical del El Escorial Madrid no 39837 and in the Catalogo del Archivo del Monasterio de San Lorenzo El Real de El Escorial page 459 no. 1475.